1. Technical Field
The present disclosure relates to a preparation method for graphitizing carbon material, in particular, to a preparation method for graphitizing the carbon material using a vacuum arc melting furnace in order to meet the demand of the graphitizing with the graphitized carbon material to be used as a negative electrode of lithium battery.
2. Description of Related Art
In a traditional isotropic graphite manufacturing process, coke is used to be mixed with coal tar pitch before being injected into a compression mold and being heat in a non-oxidation condition to around 1000 degrees Celsius to form porous amorphous carbon. The pores of the porous amorphous carbon may be filled by the coal tar pitch soaking and re-baking multiple times, after which heat processing may be applied to produce high-density amorphous carbon.
With the energy-storing technology rapidly developing, the isotropic graphite material that is of high density, high strength, high purity, and being readily tooling-prone has been in high demand. Due to the complexity of the corresponding manufacturing process, the graphite produced by the traditional approach rarely satisfies the quality demand. Recently, other manufacturing approaches taking advantage of MESO-carbon micro-beads capable of self-sintering without any mixing, kneading, or smashing, and requiring no coal tar soaking and re-baking to fill the pores. The mechanical characteristics of the isotropic graphite have improved and the corresponding manufacturing has been simplified.
In order to use such recently developed method for preparing the graphite carbon material, one high-temperature furnace for graphitizing along with heat exchange arrangement are necessary to heat the chamber, maintain the operating temperature, and protect the main body of the carbon material. The heat transmission, the maintaining of the operating temperature and the rate of the temperature increasing are subject to the efficiency of the transfer of the heat, requiring a long period of time for the graphitizing to be completed. For example, the graphitizing using the above-mentioned approach may require 1-10 hours to conclude, rendering difficult the maintaining of the operating temperature. At the same time, the crucible used in the process may not ensure such long hours of the operation, negatively affecting the characteristics of the end product of the manufacturing process.
Other disadvantages include: (1) being time-consuming, requiring significant amount of energy, needing additional devices to maintain the operating temperature, which adds extra cost to the implementation of the melting furnace, being limited in the mass production performance, and eventually increasing the corresponding manufacturing cost; (2) being difficult in better utilizing the heat applied at the expense of the heat efficiency and energy consumption when the furnace could not operate without interruption; (3) reaching 2300 degrees Celsius as its maximum temperature, which fails to be fully graphitizing the carbon material as 3200 degrees Celsius is required as theoretically suggested, and therefore makes it difficult to meet the quality standard of the ideal graphite; and (4) virtually impossible for automation with the complicated arrangement for heating electrodes and temperature maintaining of the corresponding furnace in addition to the placement and the extraction of the carbon material.
Thus, the present disclosure that uses the vacuum arc melting furnace to heat the carbon material could be one of the better options to be considered. The present disclosure preparation method could be realized by having the operating temperature reach at no less than 3200 degrees Celsius in a relatively short period of time because of the temperature increasing capability of the melting furnace, not only shortening the time for the graphitizing but also ensuring the carbon material to be fully graphitized in each and every attempt.